The ability of the nervous system to perform complex tasks such as sensory perception, learning, and coordinated movement relies on the dynamic release of neurotransmitters at chemical synapses. The secretion of neurotransmitters involves a tightly regulated process of trafficking synaptic vesicles to the plasma membrane of nerve terminals where they fuse and release neurotransmitters onto postsynaptic receptors. A key component in the regulation of synaptic dynamics is the ability of the neuron to control the number of fusable synaptic vesicles. A family of proteins, synapsins, is proposed to play a role in this regulation. This proposal's goal is to further elucidate the function(s) of synapsins. Aim I will address the differential function of synapsin I and II and whether their function is ATP-dependent through mutations affecting ATP binding. Aim II will determine whether phosphorylation of synapsins by protein kinase A is necessary for the movement of synaptic vesicles into a 'readily releasable' state. Aim III will identify a function for the conserved synapsin E domain and proteins that bind to this domain. Knowledge of protein function in neurotransmission may help elucidate the cause of disease related synaptic dysfunction.